A method of data transmission includes transmitting a magnetic signal that is modulated with the bit stream, the magnetic signal having a nominal frequency and being formed of a high frequency and a low frequency, the nominal frequency being the average frequency of the magnetic signal. The bit stream is modulated onto the magnetic signal by encoding the bit stream into the magnetic signal, where each bit in the bit stream is represented by a transition between adjoining data symbols formed of K repetitions of a first state or a second state. The first state of the pair of states includes M/2 cycles of the nominal frequency with a signal at the high frequency and M/2 cycles of the nominal frequency with a signal at the low frequency. The second state is complementary to the first state.
Legal claims defining the scope of protection, as filed with the USPTO.
determining data to be transmitted; generating a bit stream based on the data to be transmitted; and transmitting a magnetic signal that is modulated with the bit stream, the magnetic signal having a nominal frequency and being formed of a first signal having a high frequency and a second signal having a low frequency, the high frequency being higher than the nominal frequency and the low frequency being lower than the nominal frequency, the nominal frequency being the average frequency of the magnetic signal, wherein the bit stream is modulated onto the magnetic signal by encoding the bit stream into the magnetic signal, where each bit in the bit stream is represented by a transition between adjoining data symbols, each of the data symbols is formed of K repetitions of one of a first state or a second state, where the first state of the pair of states includes M/2 cycles of the nominal frequency with a signal at the high frequency and M/2 cycles of the nominal frequency with a signal at the low frequency, and where a second state of the pair of states includes signals complementary to the first state. . A method of transmitting digital data from a sonde, comprising:
Complete technical specification and implementation details from the patent document.
This application is a Continuation application of U.S. application Ser. No. 18/419,187, filed on Jan. 22, 2024, which is incorporated herein by reference in its entirety.
The present disclosure is related to co-pending and commonly-owned U.S. nonprovisional application Ser. No. 18/419,250, filed on the same day, Jan. 22, 2024, which is herein incorporated by reference in its entirety.
The current application is related to transmission of data on a low frequency magnetic field, for example transmission of data from a sonde to an above ground receiver on the magnetic field generated by the sonde.
Underground utility location and utility installation are common problems for utility companies and local municipalities. Several solutions have been developed to address these problems. In one case, where location of an underground cable or conducting pipeline is needed, an underground pipe and cable location system (often termed a line locator system) can be used. In that system, an above ground receiver detects magnetic signals transmitted by the underground pipe or cable in order to locate the pipe or cable. In another system, a sonde placed within a pipe or as part of a drilling rig can emit electromagnetic radiation that is detected by the above ground receiver to locate the position of the sonde. In some cases, markers can be located proximate the utility and are then used to locate the utility. The current disclosure is directed towards operations that involve locating an underground sonde, which for example is located in a pipe or included in a drill string.
Utility Locators comprising a signal source (Transmitter or Sonde) and a remote locator (Receiver) are well known and used within industry sectors who manage buried assets. The principle of emitting an electromagnetic field from a sonde and then locating the sonde with an above-ground receiver is well used. In the simplest applications the sonde emits sinewave signals that allow phase sensitive measurement of the resulting magnetic fields with the receiver. Receivers engaged in sonde location often include an array of spaced apart antennas (typically between 2 and 6 antennas) and can use the principles of phase coherence to derive directional and distance information to the sonde by correlating the measured signals and their relative phases.
Superimposing a low frequency data stream on to a sinewave carrier has some useful and additional applications for a locating system. In particular status information from the sonde can be communicated to the receiver. However, there are significant problems with the magnitude and phase of a dipole-shaped low frequency magnetic field, which can be emitted by the sonde, that can be provide degradation in the location measurement and further provides problems for transmission of digital data using the low frequency magnetic field.
Consequently, there is a need for better digital data communications between an underground sonde and an aboveground receiver.
In accordance with embodiments of the present disclosure, a method of transmitting digital data from a sonde is presented. The method includes determining data to be transmitted; generating a bit stream based on the data to be transmitted; and transmitting a magnetic signal that is modulated with the bit stream, the magnetic signal having a nominal frequency and being formed of a first signal having a high frequency and a second signal having a low frequency, the high frequency being higher than the nominal frequency and the low frequency being lower than the nominal frequency, the nominal frequency being the average frequency of the magnetic signal, wherein the bit stream is modulated onto the magnetic signal by encoding the bit stream into the magnetic signal, where each bit in the bit stream is represented by a transition between adjoining data symbols, each of the data symbols is formed of K repetitions of one of a first state or a second state, where the first state of the pair of states includes M/2 cycles of the nominal frequency with a signal at the high frequency and M/2 cycles of the nominal frequency with a signal at the low frequency, and where a second state of the pair of states includes signals complementary to the first state.
In some embodiments, transitions representing a digital one bit is encoded with a first data symbol of the adjoining symbols formed with the first state and a second data symbol of the adjoining symbols formed with the first state or the first data symbol formed with the second state and the second data symbol formed with the second state.
In some embodiments, transitions representing a digital zero bit is encoded with the first data symbol formed with the first state and the second data symbol formed with the second state or the first data symbol formed with the second state and the second data symbol formed with the first state.
In some embodiments, the bit stream is formed into a continuous sequence of data frames, each data frame being formed with a separator followed by a synchronization field and one or more data fields, the synchronization field and the one or more data fields separated by a separator. In some embodiments, the separator bits are zero and the synchronization bits are all ones. In some embodiments, the frame further includes a cyclic redundancy check (CRC) field separated from the last data field by a separator.
In some embodiments, the method further includes reading pitch and roll data from the sonde and encoding the pitch and roll data into the one or more data fields. In some embodiments, the one or more data fields includes a first data field, a second data field, and a third data field. In some embodiments, pitch data is presented in the first data field and the second data field while roll data is presented in the third data field.
In some embodiments, the first state includes M/4 cycles of signal at the high frequency followed by M/2 cycles of signal at the low frequency and then M/4 cycles of signals at the high frequency; and wherein the second state includes M/4 cycles of signal at the low frequency followed by M/2 cycles of signal at the high frequency and then M/4 cycles of signals at the low frequency.
In accordance with some embodiments, a method of transmitting data from a sonde is presented. The method includes measuring parameters associated with the sonde with sensors in the sonde; encoding the parameters into a data frame, the data frame having a sequence of bits, the data frame including a separator followed by a synchronization field and one or more data fields separated by separators; determining a sequence of data symbols to represent the data frame, each of the sequence of bits in the data frame being represented by transitions between adjacent data symbols in the sequence of data symbols, the data symbols each being formed by K repetitions of a first state or formed by K repetitions of a second state, where the first state includes M/2 cycles of a nominal frequency with a high frequency signal at a high frequency and M/2 cycles of the nominal frequency with a low frequency signal at a low frequency, the high frequency being higher than the nominal frequency and the low frequency being lower than the nominal frequency such that the average signal is at the nominal frequency; and transmitting a magnetic signal formed from the sequency of data symbols.
In some embodiments, transitions representing a digital one bit is encoded with a first data symbol of the adjoining symbols formed with the first state and a second data symbol of the adjoining symbols formed with the first state or the first data symbol formed with the second state and the second data symbol formed with the second state. In some embodiments, transitions representing a digital zero bit is encoded with the first data symbol formed with the first state and the second data symbol formed with the second state or the first data symbol formed with the second state and the second data symbol formed with the first state. In some embodiments, the bit stream is formed into a continuous sequence of data frames, each data frame being formed with a separator followed by a synchronization field and one or more data fields, the synchronization field and the one or more data fields separated by a separator. In some embodiments, the frame further includes a cyclic redundancy check (CRC) field separated from the last data field by a separator. In some embodiments, the separator bits are zero and the synchronization bits are all ones
In some embodiments, the method includes reading pitch and roll data from the sonde and encoding the pitch and roll data into the one or more data fields. In some embodiments, the one or more data fields includes a first data field, a second data field, and a third data field. In some embodiments, pitch data is presented in the first data field and the second data field while roll data is presented in the third data field.
In some embodiments, the first state includes M/4 cycles of signal at the high frequency followed by M/2 cycles of signal at the low frequency and then M/4 cycles of signals at the high frequency; and wherein the second state includes M/4 cycles of signal at the low frequency followed by M/2 cycles of signal at the high frequency and then M/4 cycles of signals at the low frequency.
In some embodiments of the present disclosure a sonde is presented. The sonde includes one or more sensors to measure parameters associated with the sonde; an antenna configured to transmit a magnetic signal; a driver coupled to drive the antenna to transmit a magnetic signal according to input signals; and a processor coupled to the one or more sensors and the driver, the processor configured to receive parameters associated with the sonde from the one or more sensors; encode the parameters into a data frame, the data frame having a sequence of bits, the data frame including a separator followed by a synchronization field and one or more data fields separated by separators; determine a sequence of data symbols to represent the data frame, each of the sequence of bits in the data frame being represented by transitions between adjacent data symbols in the sequence of data symbols, the data symbols each being formed by K repetitions of a first state or formed by K repetitions of a second state, where the first state includes M/2 cycles of a nominal frequency with a high frequency signal at a high frequency and M/2 cycles of the nominal frequency with a low frequency signal at a low frequency, the high frequency being higher than the nominal frequency and the low frequency being lower than the nominal frequency such that the average signal is at the nominal frequency; and communicate the input signal corresponding to the sequence of data symbols to the driver. In some embodiments, the parameters include roll and pitch data.
In some embodiments, the first state includes M/4 cycles of signal at the high frequency followed by M/2 cycles of signal at the low frequency and then M/4 cycles of signals at the high frequency; and wherein the second state includes M/4 cycles of signal at the low frequency followed by M/2 cycles of signal at the high frequency and then M/4 cycles of signals at the low frequency.
In some embodiments of the present disclosure, a method of receiving digital data from a magnetic signal transmitted by a sonde is presented. The method includes receiving a magnetic signal transmitted by the sonde, the magnetic signal having a nominal frequency and being formed of a first signal having a high frequency and a second signal having a low frequency, the high frequency being higher than the nominal frequency and the low frequency being lower than the nominal frequency, the nominal frequency being the average frequency of the magnetic signal; digitizing the magnetic signal to provide a digitized magnetic signal; and processing the digitized magnetic signal to recover a bit stream, where each bit in the bit stream is represented by a transition between adjoining data symbols, each of the data symbols is formed of K repetitions of one of a first state or a second state, where the first state of the pair of states includes M/2 cycles of the nominal frequency with a signal at the high frequency and M/2 cycles of the nominal frequency with a signal at the low frequency, and where a second state of the pair of states includes signals complementary to the first state.
In some embodiments, processing the digitized magnetic signal to recover the bit stream includes demodulating the magnetic signal to determine phase relative to a nominal signal, the nominal signal being at the nominal frequency; determining a sequence of data symbols; and determining the transitions between adjacent data symbols to determine the bit stream.
In some embodiments, demodulating the magnetic signal includes mixing the digitized magnetic signal with a sine and a cosine wave at a carrier frequency to obtain an in-phase and a quadrature signal; filtering the in-phase and the quadrature signal with decimator filters; mixing output signals from the decimator filters with the in-phase and quadrature signals to generate sub-carrier channel signals BX[I] and BX[Q]; combining the sub-carrier signals BX[I] and BX[Q] to form a cross product signal; mixing the cross product signal with a sine and cosine signal at a subcarrier frequency; filtering signals from the from the cross-product with a decimating filter to provide demodulated signals; and generating demodulated magnitude and phase signals from the demodulated signals. In some embodiments, the method further includes combining the sub-carrier channel signals BX[I] and BX[Q] from a plurality of magnetic signals before combining to form the cross product signal.
In some embodiments, receiving the magnetic signal includes receiving magnetic signals from a triaxial antenna, the triaxial antenna producing signals related to the magnetic field in two orthogonal horizontal directions and a vertical direction, and wherein combining the sub-carrier channel signals includes generating sub-carrier channel signals for each of the signals; and combining the sub-carrier channel signals for each of the signals to generate the combined sub-carrier channel signals.
In some embodiments, transitions representing a digital one bit is encoded with a first data symbol of the adjoining symbols formed with the first state and a second data symbol of the adjoining symbols formed with the first state or the first data symbol formed with the second state and the second data symbol formed with the second state.
In some embodiments, transitions representing a digital zero bit is encoded with the first data symbol formed with the first state and the second data symbol formed with the second state or the first data symbol formed with the second state and the second data symbol formed with the first state.
In some embodiments, the bit stream is formed into a continuous sequence of data frames, each data frame being formed with a separator followed by a synchronization field and one or more data fields, the synchronization field and the one or more data fields each separated by a separator. In some embodiments, the separator is a zero bit and the synchronization field includes all ones. IN some embodiments, the frame further includes a cyclic redundancy check (CRC) field separated from the last data field by a separator.
In some embodiments, the one or more data fields include a first data field, a second data field, and a third data field. In some embodiments, pitch data is presented in the first data field and the second data field while roll data is presented in the third data field.
In some embodiments, the first state includes M/4 cycles of signal at the high frequency followed by M/2 cycles of signal at the low frequency and then M/4 cycles of signals at the high frequency; and wherein the second state includes M/4 cycles of signal at the low frequency followed by M/2 cycles of signal at the high frequency and then M/4 cycles of signals at the low frequency.
In accordance with some embodiments of the present disclosure, a receiver is presented. In some embodiments, the receiver includes one or more antennas, each of the one or more antennas producing one or more signals related to a magnetic signal generated by a sonde; an analog front end that receives and digitizes each of the one or more signals from each of the one or more antennas; and a digital processor configured to receive the digitized signals from the analog front end and recovering digital data modulated onto the magnetic field generated by the sonde, wherein the magnetic signal is modulated according to a bit stream, the magnetic signal having a nominal frequency and being formed of a first signal having a high frequency and a second signal having a low frequency, the high frequency being higher than the nominal frequency and the low frequency being lower than the nominal frequency, the nominal frequency being the average frequency of the magnetic signal, and wherein the bit stream is modulated onto the magnetic signal by encoding the bit stream into the magnetic signal, where each bit in the bit stream is represented by a transition between adjoining data symbols, each of the data symbols is formed of K repetitions of one of a first state or a second state, where the first state of the pair of states includes M/2 cycles of the nominal frequency with a signal at the high frequency and M/2 cycles of the nominal frequency with a signal at the low frequency, and where a second state of the pair of states includes signals complementary to the first state.
In some embodiments, the digital processor is configured to identify transitions representing a digital one bit that is encoded with a first data symbol of the adjoining symbols formed with the first state and a second data symbol of the adjoining symbols formed with the first state or the first data symbol formed with the second state and the second data symbol formed with the second state. In some embodiments, the digital processor is configured to identify transitions representing a digital zero bit that is encoded with the first data symbol formed with the first state and the second data symbol formed with the second state or the first data symbol formed with the second state and the second data symbol formed with the first state.
In some embodiments, the bit stream is formed into a continuous sequence of data frames, each data frame being formed with a separator followed by a synchronization field and one or more data fields, the synchronization field and the one or more data fields separated by a separator. In some embodiments, the separator bits are zero and the synchronization bits are all ones. In some embodiments, the frame further includes a cyclic redundancy check (CRC) field separated from the last data field by a separator.
In some embodiments, the processor further includes reading pitch and roll data from the sonde and encoding the pitch and roll data into the one or more data fields. In some embodiments, the one or more data fields include a first data field, a second data field, and a third data field. In some embodiments, the digital processor is configured to recover pitch data that is presented in the first data field and the second data field and roll data that is presented in the third data field.
In some embodiments, the first state includes M/4 cycles of signal at the high frequency followed by M/2 cycles of signal at the low frequency and then M/4 cycles of signals at the high frequency; and wherein the second state includes M/4 cycles of signal at the low frequency followed by M/2 cycles of signal at the high frequency and then M/4 cycles of signals at the low frequency.
In some embodiments, the digital processor recovers digital data based on a single signal from one of the antennas. In some embodiments, one of the antennas is a triaxial antenna and the digital processor is configured to recover digital data based on three signals from the triaxial antenna.
These and other embodiments will be described in further detail below with respect to the following figures.
The drawings may be better understood by reading the following detailed description.
In the following description, specific details are set forth describing some aspects of the present invention. It will be apparent, however, to one skilled in the art that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are meant to be illustrative but not limiting. One skilled in the art may realize other elements that, although not specifically described here, are within the scope and the spirit of this disclosure. Such modifications may include substitution of known equivalents for any aspect of the disclosure in order to achieve the same result in substantially the same way.
Consequently, this description illustrates inventive aspects and embodiments that should not be taken as limiting—the claims define the protected invention. Various changes may be made without departing from scope of this description and the claims. In some instances, well-known structures and techniques have not been shown or described in detail in order not to obscure the invention.
Unless the context requires otherwise, throughout the present specification and claims, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is as “including, but not limited to.” Recitation of numeric ranges of values throughout the specification is intended to serve as a shorthand notation of referring individually to each separate value falling within the range inclusive of the values defining the range, and each separate value is incorporated in the specification as it were individually recited herein. Further, individual values provided for particular components are for example only and are not considered to be limiting. Specific dimensional values for various components are there to provide a specific example only and one skilled in the art will recognize that the aspects of this disclosure can be provided with any dimensions. Additionally, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment, but may be in some instances. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
Embodiments of the present disclosure include a novel method of encoding and decoding digital information onto a low frequency alternating magnetic field, such as that transmitted by an underground sonde. Embodiments of this disclosure offer advantages over existing encoding and decoding methods and can be extended to include 3D orthogonal axis sensors. Embodiments of the present disclosure have applications for a sonde signal used in Horizontal Directional Drilling and Push Rod Boring systems. Other applications exist in the field of general pipe and cable locating, such as is described in U.S. application Ser. No. 18/419,250, which is concurrently filed with the present application and is herein incorporated by reference in its entirety.
Embodiments of data encoding according to the present disclosure has multiple advantages over existing encoding and decoding methods and can be implemented on any antenna system or antenna array, including arrays with one or more 3D orthogonal axis sensors. Embodiments of sonde locating system including this encoding system are described below. Some embodiments of this disclosure provide real-time ‘on-the-fly’ data rather than separated data and command modes.
Embodiments of the present disclosure include a data coding scheme with an identified signal modulation that does not affect the locate field shape. The scheme is described in the context of a Sonde communicating pitch and roll information for a directional boring application using any antenna configuration, but the general idea, as a low bandwidth data mechanism applies equally to other applications.
Installing underground utility cable or pipe using a steerable boring tool is well known. The so called trenchless Horizontal Directional Drilling (HDD) system has the obvious advantage of being less disruptive on the surface, as compared to traditional excavation techniques. Significant developments in the art have facilitated accurate positional feedback so that operators can direct and control the drilling or boring operation. The method is not confined to drilling as some systems use push rods forced by hydraulic actuators to direct the drill string and head underground.
1 FIG.A In each of these cases, accurate location of the drill head is desired in order to direct the drill head along the desired route for the cable or pipe being installed. One technique to provide positional feedback is to place a sonde in the drilling or boring head. The sonde then emanates a low frequency alternating magnetic field, which is typically a dipole field in shape. The location of the sonde can then be determined using an above-ground receiver to detect the low frequency alternating magnetic field. An illustration of an example of this system is illustrated in.
1 FIG.A 1 FIG.A 1 FIG.A 1 FIG.B 100 112 114 114 118 112 118 114 114 114 112 120 112 116 116 112 illustrates a boring systemthat uses a sondein positioned proximate to the drill head. As illustrated in, drill headis attached to a drill string. Sondeis located in the drill stringadjacent to drill head, or in drill headitself. Drill headand sondeare underground, under surfaceas illustrated in. As is illustrated, Sondeemits an electromagnetic field, which as discussed above can be a low-frequency dipole magnetic field.further illustrates a dipole field, which can be generated with a dipole antenna within sonde.
102 120 102 104 106 108 104 106 108 106 108 102 110 1 FIG.A Receiveris locating above surfaceand usually can be handheld by an operator. Typically, receiverincludes a wandwhere one or more antennas are positioned. Antennas in this antenna array can be spaced apart in both horizontal and vertical configurations in order to map the magnetic field. In the example of, antennasandare positioned within wand. Antennasandcan each be 3-D antennas (also referred to as triaxial antennas), but combinations of 2-D antennas and 1-D antennas can be used. A 3-D antenna, or triaxial antenna, can include three individual coils that are positioned relative to one another to measure magnetic fields in three orthogonal directions at a point at the center of the antenna. Signals from antennasandcan be processed within receiverand the results displayed on a user interface.
112 122 118 114 122 114 102 102 122 122 112 In some examples, the results can include the determination of the position of sonde. This positional data can be transmitted to the drill controllerthat controls drill stringand drill head. The drill controllercan steer drill headbased on the positional data received from receiver. In some embodiments, receiverand controllercan be in communication so that controllercan receive accurate data regarding the position of sonde.
2 2 FIGS.A andB 1 FIG.A 2 FIG.A 200 102 200 202 202 204 206 206 204 204 202 202 206 illustrate an example of a receiver, that can be an example of receiveras illustrated in. As shown in, receiverincludes a wand. Wandincludes an antenna sectionand an electronics section. Electronics sectioncan include digital circuitry, microprocessors, ASICs, memory, filters, A/D converters, and all other electronics that process the signals received from antennas housed in antenna section. The antennas distributed within antenna section, as discussed above, can be antennas any combination of 3-D, 2-D, and 1-D antennas spaced relative to each other in a direction along the length of wandand in a direction perpendicular to wandto provide both vertical and horizontal data to electronics section.
200 208 210 208 202 210 210 206 202 Receiverincludes a handle sectionand a user interface. Handle sectionis connected between wandand user interface. User interfacedisplays the results of the data processing performed in electronics sectionof wand.
2 FIG.B 210 200 illustrate an example of user interface. For demonstrative purposes, the user interface of a Vloc3-Pro receiver (produced by Vivax Metrotech Corp.) in Sonde mode. However, receivercan be adapted to operate according to aspects of the present disclosure.
2 FIG.B 210 214 216 212 218 219 220 222 224 222 216 218 112 200 210 As illustrated in, user interfacedisplays a peak signal detector, a signal strength bar graph, a sonde icon, a null point, a directional arrowthat indicates the direction to the detected sonde, a frequency selection, a numeric signal level, and a gain setting. The numeric signal levelmirrors the signal strength bar graph. As is understood from the electromagnetic field pattern around a sonde, there are two null points ahead and behind the sonde (one of which is indicated by null point) and the sonde is located at a maximum of the field strength. In some embodiments, sondecan emit electromagnetic fields at a frequency selected from a number of different frequencies (or tones). The locatoris tuned to the frequency that the sonde is locating. Consequently, using the data displayed on user interfacean operator can, once the electromagnetic field from the sonde is detected, locate the point above the surface under which the sonde is located. Given the signal strength and other characteristics, the depth of the sonde can also be determined.
200 112 200 100 200 226 112 222 204 219 112 112 212 218 1 FIG.A 2 FIG.B Consequently, the system that includes receivergives a clear graphical representation of the position of a Sonderelative to receiverin a locating systemas illustrated in. As shown in, receivercan also calculate and show the depthof the Sondeand a strength indicatorof the signal strength received. The receiver can use two sets of tri-axial antennas located in antenna portionto give an omni locate bar-graph and without the ‘nulls’ which cause confusion in locating instruments equipped with only four (4) sensors. The guidance arrow(s)lead to the target sondeon a path that automatically aligns the user on the axis of the sonde. The sonde iconindicates the sonde position and field alignment. The Null positions (intrinsic to the dipole field) are indicated by the null point. In this system the sonde can be in any orientation, even vertical.
114 As discussed above, existing Horizontal Boring applications make use of the data transmitted by the Sonde to provide feedback to an operator, which allows the operator to steer the drill along the required path. The drill head direction can be controlled by controlling the pitch angle and roll angle of the drilling head. The pitch angle is the angle that the drilling or cutting head axis makes with respect to a level surface perpendicular to the direction of gravity. The roll angle is the rotation angle of the drilling or cutting head about its axis with respect to the direction of gravity.
112 114 114 112 102 200 The axis of sondecan be the same as that of drilling head. Consequently, the pitch and roll of the sonde can be the same as that of the drilling head. Consequently, pitch and roll may be among the data that would be useful to transmit from sondeto receiver, e.g. receiver.
112 200 Whilst many encoding and decoding systems can convey digital information on a suitable carrier, there are consequential problems to the magnitude and phase of a low frequency magnetic field. These problems cause degradation of the primary purpose of a locating instrument-accurate pin-point locating and depth measurement. In particular, traditional Amplitude Modulated Manchester Bi-Phase encoding has a detrimental effect on the ability to locate sondewith receiver.
1 FIG.B 1 FIG.B Conventional data transmission between the sonde and the transmitter may result in multiple difficulties. The dipole magnetic field which emanates from a Sonde as illustrated inis a well-known shape. The field geometry illustrated incauses problems when the electromagnetic field emitted by the sonde is processed by a 3D sensor array of the receiver, which provides a response according to three (3) orthogonal axes. In particular, there are points where one or more sensors may experience a null and a phase reversal, which causes difficulty in retrieving digital data. Movement of the locator causes individual sensors to rotate and translate their relative position in the magnetic field and this can lead to multiple phase reversals being encountered. Given these problems, there is a need for a data encoding and decoding system which can overcome these issues, without causing a discontinuity to the user interface or indeed to the decoded data.
Consequently, there are identified needs for improvement. Embodiments of the present disclosure address one or more of these needs. Some embodiments of the present disclosure may provide a waveform and data encoding system that runs in continuous wave, without the need to separate a data mode from a general locating mode. Some embodiments of the present disclosure may provide a waveform and data encoding scheme that allows data decoding even when a phase discontinuity or phase reversal on one or more of the orthogonal sensors occurs. Some embodiments of the present disclosure may provide a waveform and data encoding scheme that avoids a drift of the average frequency of the carrier. Some embodiments of the present disclosure may provide a waveform and data encoding scheme that can be phase and/or frequency tracked such that the encoded data waveform does not cause a net phase or frequency drift. Some embodiments of the present disclosure may provide a waveform and data encoding scheme that is balanced over a cycle of the sub-carrier. Some embodiments may of the present disclosure provide a waveform and data encoding scheme that guarantees phase coherence between the transmitter and receiver. Some embodiments of the present disclosure may provide a waveform and data encoding scheme which ensures there is negligible loss of signal-to-noise ratio when compared with a pure sinewave transmission. Some embodiments of the present disclosure may provide a waveform and data encoding scheme which does not impose periodic step response (Heaviside Step Function) on the Digital Signal Processing and associated filter history.
118 200 200 118 202 202 The signal tone is modulated as discussed below so that sondecan also transmit digital information to receiver. In embodiments of the present disclosure, the modulation is implemented in such a way that there is practically no disturbance to the signal locating tone, and therefore does not interfere with the ability of receiverto locate sonde. Further, since the modulation is provided on the signal locating tone (as a frequency shift key (FSK) based around the signal locating tone), each of the antennas in antenna sectionprovides a signal that includes the modulation. Signals from one or more of the antennas in antenna sectioncan be used to demodulate the modulated signal and recover the transmitted data.
3 3 FIGS.A andB 3 FIG.C 3 FIG.C 1 FIG.B 1 FIG.A 300 340 340 342 344 340 340 344 344 346 346 348 344 344 340 344 346 340 348 340 112 illustrate a receiverandillustrates a sondeaccording to some embodiments of the present disclosure. As shown in, sondecan includes sensorsthat provide data to processor. Sensorscan include pitch and roll sensors as well as other sensors, for example environmental sensors. Sensorsalso includes analog processing and digitizing circuitry to provide digital data to processor. Processoris coupled to a driver. Driverprovides a signal to drive a dipole antennato generate a dipole field as illustrated inat a particular frequency, or tone, which is selected by processor. Processorcan be preset to generate fields of a particular frequency prior to deployment or can generate fields at a frequency that is communicated to sondein other ways. Processorcan also provide digital data to driver, which is modulated onto the tone generated by sondeand transmitted via the dipole field from antenna. A modulation method according to embodiments of the present disclosure is further described below. Sondecan replace sondein.
344 344 342 346 348 In particular, processorcan include any combination of microprocessors, microcomputers, discrete digital circuitry, application specific integrated circuits (ASICs), volatile and non-volatile memory, or other components to perform as described here. In particular, processorcan receive measured parameters from the one or more sensors of sensors, compiles the parameters into a digital bit stream as described below, and provides input signals to driverthat controls magnetic signal transmitted by antenna.
3 FIG.A 3 FIG.C 3 FIG.A 3 FIG.A 300 300 340 300 302 300 304 306 302 304 306 304 306 340 illustrates a receiveraccording to some embodiments of the present disclosure. Receiveraccording to embodiments of the present disclosure can locate and receive digital data from sondeas illustrated in. As illustrated in, receivercan include multiple antennas geometrically distributed within a wand. In the example illustrated in, receiverincludes two antennas, antennasand, although there may be any number of antennas of any type distributed within wand. In some embodiments, antennasandcan each be triaxial antennas, each with multiple coils oriented to measure the magnetic field along each of three orthogonal axis. Antennasanddetect the electromagnetic fields that are transmitted by sonde.
3 FIG.A 2 FIG.A 2 FIG.B 304 306 302 308 304 306 310 310 340 312 312 312 340 340 312 314 340 300 200 314 As is illustrated in, signals from antennasandin wandare input to electronics section. In particular, the signals from antennasandare input to an analog front end (AFE)for analog processing. AFEcan receive signals transmitted by sonde, provide some analog filtering to the received signals, and digitize the signals with an analog-to-digital converter. A digital processing circuitreceives and processes the digitized signals as discussed in further detail below. In particular, digital processing circuitcan be any combination of microprocessors, microcomputers, discrete digital circuitry, application specific integrated circuits (ASICs), volatile and non-volatile memory, or other components that perform the functions as described here. In particular, digital processing circuitdigitally process signals at the particular frequency of sondeand further demodulates and receives digital data that is transmitted with the magnetic fields transmitted by sonde. Digital processing circuitis coupled to user interfaceto display locate information and sonde data to a user, and may transmit data to a controller of sonde. Receivercan be similar to receiverillustrated inand user interfacecan be similar to that displayed in.
340 300 340 300 340 300 Sondeand receiverare configured such that sondeis set to transmit an electromagnetic field according to a selected tone and receiveris set to receive the electromagnetic field according to the selected tone. Further, sondeand receiverare configured to exchange data using the selected tone as is further described below.
340 340 300 340 340 300 300 340 340 In particular, sondegenerates an oscillating magnetic field in a narrow bandwidth that constitutes the signal tone. The signal tone allows sondeto be located by a magnetic field locating device (locator) such as receiver, as discussed above. Sondemay be programmed to operate on a plurality of selectable tones. Sondeand receiverare then tuned to the same tone so that receivercan receive the electromagnetic field generated by sondeand thereby locate sonde.
340 300 300 340 The signal tone is modulated as discussed below so that sondecan also transmit digital information to receiver. In embodiments of the present disclosure, the modulation is implemented in such a way that there is practically no disturbance to the signal locating tone, and therefore does not interfere with the ability of receiverto locate sonde.
3 FIG.B 3 FIG.B 300 334 302 334 334 1 2 300 300 illustrates a more detailed example of receiveraccording to some embodiments of the present disclosure. The example illustrated inshows processing of signals from an example antenna, which is one of the antennas in wand. In this example, antennais a triaxial antenna formed from three concentric, orthogonal magnetic field coils to measure the magnetic field strength in three orthogonal directions. Consequently, antennaproduces three signals related to the magnetic field strengths in two orthogonal horizontal directions (BHand BH) and the magnetic field strength in the vertical direction (BV). It should be noted that the terms “horizontal” and “vertical” relate to the physical positioning of receiverand will correspond to geographic horizontal and vertical positions only if receiveris physically oriented accordingly.
1 2 310 308 1 316 318 2 320 316 318 320 316 318 320 322 324 326 322 324 326 1 2 328 328 334 302 340 322 324 326 330 334 330 1 2 330 1 2 302 The signals BH, BH, and BV are input to AFEin electronic section. As is illustrated, signal BHis input to AFE, BV is input to AFE, and BHis input to AFE. As discussed above, each of AFE, AFE, and AFEprovide analog filtering and digitization of the respective signals. The digital signals from AFE,, andare input to signal processing,, and. Signal processing,, andprocess each of the digitized signals BH, BV, and BH, respectively, to recover signal magnitude and phase, which is input to locate processing. Locate processingprocesses the magnitudes and phases of the magnetic field signals detected by, as well as the signals received from other antennas in wand, to determine the location of sondebased on those signals. Signals from signal processing,, andcan also be input to data demodulatorwhere the digital data modulated onto the magnetic signals measured by antennais recovered. In some embodiments, data demodulatorrecovers the digital data based on one of the signals BH, BV, or BH. In some embodiments, data demodulatorrecovers the digital data based on a combination of all of the signals BH, BV, and BH. In some embodiments, data from multiple antennas in wandcan be used to recover the digital data.
340 340 340 High low High nom Low nom avg nom As is discussed above, sondemodulates data onto the generated electromagnetic field. As discussed in further detail below, in the implemented modulation according to the present disclosure, the frequency of the electromagnetic field generated by sondeswitches between two frequencies, fand f. The first frequency, f, is slightly above the nominal signal frequency fof the tone and the second frequency, f, is slightly below the nominal signal frequency fof the tone. In accordance with aspects of the present disclosure, the average frequency fover time of the electromagnetic field generated by sondeis f.
High Low High low High low High Low low High The phase of the signal relative to the nominal signal tone thus ramps up during transmission of signals at fand ramps down during transmission of frequencies at frequency f. This ramping up and down can be used to construct a data sub-carrier, the phase of which encodes information as explained in more detail below. In this modulation scheme sub-carrier cycle can be composed of M signal tone cycles and can exist in one of two phase states, referred to as positive (P) and negative (N). In general, each of the two phase states includes M/2 signal tone cycles at frequency fand M/2 signal tone cycles at frequency f. The signals at fand fcan be distributed in any fashion through the M signal tone cycles and consequently the phase of the signal relative to the nominal signal is the same at the end of the M cycles as it was at the beginning of the M cycles, for example zero. The two phase states are complementary in that where, in the M cycles, the first phase is generating a signal at frequency fthe second phase is generating a signal at frequency f, and where the first phase is generating a signal at frequency fthe second phase is generating a signal at frequency f.
High low High Low High low high low In some embodiments, for example, the P state consists of M/4 cycles at frequency ffollowed by M/2 cycles at frequency fand then M/4 cycles at frequency f. It is thus convenient, but not essential, for M to be a multiple of 4. The N state consists of M/4 cycles at frequency ffollowed by M/2 cycles at frequency fand then M/4 cycles at frequency f. Note that the frequency cycles of fand fin the N state are transposed relative to the P state. This represents an example carrier scheme, but other carrier schemes can be devised such that the average frequency over the carrier scheme is the nominal frequency for the tone and the N-state and P-states of the carrier scheme are transposed.
4 4 FIGS.A andB 4 FIG.A 400 402 404 400 406 402 400 nom high low high high low high low high High low illustrate states P and N for a subcarrier scheme with M=16 cycles, as described above. As illustrated in, a P-stateis illustrated. Nominal signalwith frequency fis illustrated for reference. The actual signal frequencyillustrates that, in P-state, there are four cycles (M/4) where the signal has frequency f, then eight cycles (M/2) where the signal has frequency f, and another four cycles (M/4) where the signal has frequency f. The phase (Φ)of the actual signal relative to nominal signalthen illustrates that during cycles where the signal is operating at frequency fthe phase increases and during cycles where the signal is operating at frequency fthe phase decreases. As a consequence, during P-Statethe phase reaches a peak after the first cycles with the signal at frequency f, a low after the cycles where the signal is at frequency f, and returns to the starting phase (which may be 0) after the second cycle with the signal at frequency f. Consequently, the distribution of cycles with fand fis symmetric so that there is no overall change in the phase over the M cycles of the P-state subcarrier scheme.
4 FIG.B 410 412 414 412 416 412 412 nom low High low low High Low High Low High low illustrate an N-stateaccording to some embodiments of this disclosure. Nominal signalwith frequency fis illustrated for reference. The actual signal frequencyillustrates that, in N-state, there are four cycles (M/4) where the signal has a frequency ffollowed by eight cycles (M/2) where the signal has a frequency f, again followed by four cycles (M/4) where the signal has a frequency f. The phase (Φ)of the signal relative to nominal signalthen illustrates that during cycles where the signal is operating at frequency fthe phase decreases and during cycles where the signal is operating at a frequency fthe phase increases. As a consequence, during N-statethe phase reaches a minimum after the first cycles with the signal at frequency f, a high after the cycles where the signals is at frequency f, and returns to the starting phase (which may be 0) after the final cycles with the signal at frequency f. Consequently, the distribution of cycles with fand fis symmetric so that there is no overall change in the phase over the M cycles of the subcarrier scheme.
4 4 FIGS.A andB High low High low High low nom It should be noted that the example illustrated inis for illustration only. The number of cycles M that can be used in the N-state and P-state can be any value. Further, there may be a different subcarrier scheme (i.e. different sequence of fand fsignals). The scheme can be expanded or modified to have different numbers of cycles or a different distribution of fand f. However, in accordance to embodiments of the present disclosure, the sequence of fand fcycles are symmetric so that at the conclusion of the subcarrier scheme the change in phase throughout the M cycles of the scheme is zero (0). Furthermore, the average frequency of the signal is at fthroughout transmission of data.
nom nom In accordance with some embodiments of the present disclosure, data symbols can be transmitted using a series of successive subcarrier schemes. In accordance with embodiments of the present disclosure, each transmitted data symbol can be indicated with an integer number K of identical sub-carrier cycles, that is either K cycles of P or K cycles of N. Consequently, in order to transmit data the signal tone frequency fis a factor of K*M higher than the data symbol rate (i.e. f=a*K*M, where a is the data symbol rate).
5 5 FIGS.A andB 5 5 FIGS.A andB 5 FIG.A 4 FIG.A 500 502 400 504 504 500 illustrate data symbols represented in K repetitions of P states or K repetitions of N states, respectively. In the example illustrated in, K is eight (8). For example, a first data symbol is formed from P states and a second data symbol can be formed of N states. In general, K can be any integer.illustrates a data symbol. In particular, the symbol frequencythat includes K=8 P-statesas illustrated in, for example. The phase changeindicates the phase change of the signal over the K*M cycles of the data symbol. As indicated, the phase changeis symmetric across the symboland results in no overall phase change (ΔΦ=0).
5 FIG.B 4 FIG.B 510 502 410 514 514 510 Similarly,illustrates a data symbolformed with K=8 N-states. The symbol frequencyincludes K=8 N-statesas illustrated in, for example. The phase changeindicates the phase change of the signal over the K*M cycles of the data symbol. As indicate, the phase changeis symmetric across data symboland results in no overall phase change (ΔΦ=0).
0 (zero)=P-N or N-P transition between successive data symbols; and 1 (one)=P-P or N-N transition between successive data symbols. In accordance with embodiments of the present disclosure, individual data bits are transmitted at the symbol rate a based on the boundary between successive data symbols. In some embodiments, a zero bit can be represented by a phase transition between two successive data symbols (P-N or N-P) and a one bit is represented by no phase transition between successive data symbols (P-P or N-N). In other words:
6 6 FIGS.A throughD 6 FIG.A 6 FIG.A 5 FIG.A 4 FIG.A 5 FIG.B 4 FIG.B 6 FIG.A 6 FIG.A 600 602 604 602 500 400 604 510 410 606 608 602 604 610 602 604 610 608 608 602 604 High low illustrate depictions of the various transitions used to represent digital bits according to some embodiments of the present disclosure.illustrates a data symbol transitionfrom P-state symbols to N-state symbols, which as discussed above can represent a digital 0 bit.illustrates two successive data symbols, symbolsand. Data symbolis a data symbolas shown in, which includes K=8 number of successive P-statesas illustrated in. Data symbolis a data symbolas shown in, which includes K=8 number of successive N-statesas shown in.illustrates the frequency of the signal(fand f) and the phaserelative to the nominal signal. Data symbolends and data symbolbegins at transition. As shown in, data symbol(that includes successive P-states) smoothly transitions to data symbol(that includes successive N-states) at transition. As is illustrated, there are no discontinuities in phase. Further, there is no overall shift in phasethrough the transition such that the phase at the start of data symbolis the same as that at the end of data symbol(i.e., ΔΦ=0).
6 FIG.B 6 FIG.B 5 FIG.B 4 FIG.B 5 FIG.A 4 FIG.A 6 FIG.B 6 FIG.B 612 614 616 614 510 410 616 500 400 618 620 614 616 622 614 616 620 620 614 616 High low illustrates a data symbol transitionfrom N-state symbols to P-state symbols, which as discussed above can represent a digital 0 bit.illustrates two successive data symbols, symbolsand. Data symbolis a data symbolas shown in, which includes K=8 number of successive N-statesas illustrated in. Data symbolis a data symbolas shown in, which includes K=8 number of successive P-statesas shown in.illustrates the frequency of the signal (fand f)and the phaserelative to the nominal signal. Data symbolends and data symbolbegins at transition. As shown in, data symbol(that includes successive N-states) smoothly transitions to data symbol(that includes successive P-states). As is illustrated, there are no discontinuities in phase. Further, there is no overall shift in phasethrough the transition such that the phase at the start of data symbolis the same as that at the end of data symbol(i.e., ΔΦ=0).
6 FIG.C 6 FIG.C 5 FIG.B 4 FIG.B 6 FIG.C 6 FIG.C 624 626 628 626 628 510 410 630 632 626 628 634 626 628 632 632 626 628 High Low illustrates a data symbol transitionfrom N-state symbols to N-state symbols, which as discussed above can represent a digital 1 bit.illustrates two successive data symbols, symbolsand. Both data symboland data symbolare illustrated as data symbolas shown in, which includes K=8 number of successive N-statesas shown in.illustrates the frequency of the signal (fand f)and the phaserelative to the nominal signal. Data symbolends and data symbolbegins at transition. As shown in, data symbol(that includes successive N-states) smoothly transitions to data symbol(that also includes successive N-states). As is illustrated, there are no discontinuities in phase. Further, there is no overall shift in phasethrough the transition such that the phase at the start of data symbolis the same as that at the end of data symbol(ΔΦ=0).
6 FIG.D 6 FIG.D 5 FIG.A 4 FIG.A 6 FIG.D 6 FIG.D 636 638 640 638 640 500 400 642 646 638 640 648 638 640 646 646 638 640 High Low illustrates a data symbol transitionfrom P-state symbols to P-state symbols, which as discussed above can represent a digital 1 bit.illustrates two successive data symbols, symbolsand. Both data symboland data symbolare illustrated as data symbolas shown in, which includes K=8 number of successive P-statesas shown in.illustrates the frequency of the signal (fand f)and the phaserelative to the nominal signal. Data symbolends and data symbolbegins at transition. As shown in, data symbol(that includes successive P-states) smoothly transitions to data symbol(that also includes successive P-states). As is illustrated, there are no discontinuities in phase. Further, there is no overall shift in phasethrough the transition such that the phase at the start of data symbolis the same as that at the end of data symbol(ΔΦ=0).
6 6 FIGS.A throughD 6 6 FIGS.A throughD High low nom The data transmission methods according to embodiments of this disclosure have several appealing features which result in the signal tone being undisturbed for practical purposes. In particular, as is indicated in, there are no phase discontinuities such as can occur with a simple FSK scheme. Further, as shown in, the signal waveform is balanced in that the total durations of signals at frequency fand signals at frequency fdo not vary with data modulation. This results in the average signal tone frequency being data independent and is always f.
6 6 FIGS.A throughD 6 FIG.A 6 FIG.B 6 FIG.C 6 FIG.D 6 FIG.A 6 FIG.B 6 FIG.C 6 FIG.D 608 620 632 646 606 618 630 642 High low nom As is illustrated in, the signal waveform is balanced in the sense that there are no overall shifts in relative phase. As pointed out above, phaseof, phaseof, phaseof, and phaseof, the peak-to-peak phase deviation remains constant and shows no phase discontinuities or phase shifts through data transition. Further, as is illustrated in signal frequencyof, signal frequencyof, signal frequencyof, and signalofhas properly balanced fand fthat the overall average signal frequency is f. The sub-carrier frequency for data transmission can also easily be set outside the signal tone locating band while still allowing a useful data rate.
7 FIG. 7 FIG. 4 FIG.A 4 FIG.B 700 702 704 702 704 706 708 706 708 710 illustrates an example of an unbalanced transitionbetween a series of P-states to a series of N-states. As shown in, signal frequencyand phaseillustrate the transition, similar to what would occur in, for example, Manchester coding. Signal frequencyand phaseillustrate a first sectionthat exhibits a series of P-state signals as illustrated above inand a second sectionthat exhibits a series of N-state signals as illustrated above in. First sectionand second sectionare separated by transition section.
710 710 702 low 1 2 2 1 As is illustrated in transition section, however, in transition sectionthe signal frequencyshows that the signal is at frequency ffor a period of time long enough that the average frequency shifts from frequency Φto frequency Φ. This is a shift in the average phase of ΔΦ=Φ−Φ. This phase shift disturbs the detected signal tone due to the unfortunate timing of the transition. The resulting phase shift ΔΦ and the disturbance in the average frequency results in signal degradation.
7 FIG. The transition illustrated incan, for example be, Manchester coding of 8 ones followed by 8 zeros (or vice versa depending on polarity). It will clearly cause a data dependent disturbance of the detected signal tone as discussed above
6 6 FIGS.A throughD nom The transitions illustrated in, as discussed above, provide for smooth transitions with no shifts in the average phase throughout transmission of data. Further, the average frequency of the signal remains at f. Consequently, the sub-carrier frequency can also easily be set outside the signal tone locating band while still allowing a useful data rate.
6 6 FIGS.A andB 6 6 FIGS.C andC 300 An advantage of using transitions to mark data zeros is as illustrated inis that the receiving device, receiver, does not need to determine the absolute phase of the sub-carrier (or indeed the signal tone) since P-to-N and N-to-P transitions are equivalent. On the other hand, if no transitions at all are detected, as is illustrated in, then this represents a stream of data ones. In some embodiments of the framing structure, this situation may not be recognized as valid data.
312 310 312 300 3 3 FIGS.A andB 8 8 FIGS.A andB The decoding stage, which can be implemented digitally in digital processingor may have components provided in both AFEand Digital processingof receiveras illustrated in, is dependent on a suitably designed data framing scheme. Embodiments of the present disclosure deploy a well-matched data framing scheme. Characteristics of such a data framing scheme can include the following: maximizing the data opportunity (the information bandwidth being sufficient to effectively transmit data); maximizing the Signal-to-Noise Ratio (SNR) and consequently the transmission distance that can be attained; allowing the decoding system to latch on to the demodulated signal, regardless of where it may start in the data frame; and guaranteeing phase markers to assist in synchronizing to the data frames. A particular example of such a frame is illustrated in.
8 FIG.A 6 6 FIGS.A throughD 8 FIG.A 800 800 802 800 802 800 802 802 804 806 810 818 806 810 814 818 808 812 816 820 818 802 804 806 802 806 802 illustrates a bit streamusing the bit representations as illustrated in. Bit streammay include a series of data framesas is further illustrated. In some embodiments, bit streammay be a continuous series of data frames. In some embodiments, bit streammay have sporadic sequences of one or more data frames. As illustrated in, data framecan include any number of individual bits, starting with a separator bitfollowed by a synchronization field, and one or more data fields data 1through data N. The synchronization fieldand the one or more data fields (data 1, data 2, through data N) are each separated by a separator (separators,, and, respectively. In some embodiments, a cyclic redundancy check (CRC) field, separated by separatorfrom the last data field data N, finishes data frame. The separatorfollowed by the synchronization fieldprovides a unique identifier that the receiver can use to identify the start of data frame. Consequently, synchronization fieldis configured such that that particular sequence of bits cannot recur elsewhere in data frame.
802 802 802 802 802 8 FIG.B 8 FIG.B For illustrative purposes, a particular example of data frameis illustrated in. In the example illustrated in, frameincludes 26 bits, however as discussed above framemay include any number of overall bits. As discussed above, framestarts with a separator followed by a synchronization field, one or more data bit fields, and a cyclic redundancy check (CRC) field, each separated by a separator. In some embodiments, the synchronization field includes a different number of bits than are included in the one or more data bit fields or the CRC field so that the synchronization field is easily distinguishable within frame.
802 802 804 806 802 806 806 808 810 810 812 814 814 816 818 818 820 822 804 808 812 816 820 806 810 814 818 822 802 802 8 FIG.A 8 FIG.A 8 FIG.B 8 FIG.B 6 6 FIGS.A andB 6 6 FIGS.C andD 8 FIG.B 1 2 3 In the particular example of bit frameillustrated in, bit framestarts with a separator bitfollowed by synchronization bits, designated as Y in. There may be any number of synchronization bits in frame, but in the example illustrated inthere are five (5) synchronization bits. Synchronization bitsare followed by another separatorand then data field, which includes four bits labeled D. Data fieldis followed by another separatorand then another data field, which includes four bits labeled D. Data fieldis followed by a separatorand a third data field, which includes four bits labeled D. Data fieldis followed by a separatorand CRC field, which includes four bits labeled C. As is illustrated in, separators,,,, andcan consist of a single bit, which in some embodiments is a 0 as illustrated in. Synchronizationcan be a five-bit field. In some embodiments, the five bits can all be a 1 as is illustrated in. Data bits,,, and CRC fieldcan be four-bit fields that will be represented as a combination of zeros and ones representing the transmitted data. In some embodiments, data can be sent continuously in fixed length frames with no gaps between frames. In the particular example of the 26-bit frame illustrated in, the data framecan have the following format:
802 In a particular frame structure applicable to sonde applications, the framestructure is defined in the following table:
Item Data Element Resource Separator S 1 bit Sync YYYYY 5 bits Separator S 1 bit Pitch Data 1 1 1 1 DDDD 4 bits Separator S 1 bit Pitch Data 2 2 2 2 DDDD 4 bits Separator S 1 bit Roll Data 3 3 3 3 DDDD 4 bits Separator S 1 bit CRC CCCC 4 bits Total 26 bits
300 806 810 814 818 822 806 810 814 818 822 806 802 810 814 818 822 802 342 340 8 FIG.B In some embodiments, the separator fields are a zero bit. The regular insertion of zero separator bits (phase inversion) allows the receiving deviceto synchronize with the bit stream. The sync fieldincludes a different number of bits than is provided in data fields,,or CRC field. In the example illustrated in, sync flagincludes five (5) bits, all of which are ones, while data fields,,and CRC fieldeach include four (4) bits. This guarantees that the sync field(for example of five ones) can only occur at the start of a frameand cannot be emulated in any of the data fields,,, or. Consequently, framecan be used to send pitch and roll data as detected by sensorsof a sonde.
342 810 814 810 814 810 814 In particular, the pitch data can be the pitch angle detected in sensorscoded in 8 bits of data fieldsand. In particular, in embodiments where data fieldsandare each 4 bit fields, the 8 data bits in data fieldsandcan represent the pitch angle in degrees as a two's complement number in the range −90 to +90. Data is generally sent most-significant-bit (MSB) first.
342 818 818 Roll data as measured by sensorscan be represented in data field. In embodiments where data fieldis a 4-bit field, 16 equally spaced roll orientation angles in increments of 22.5 degrees can be represented.
822 806 810 814 818 320 804 820 822 The CRC fieldallows for an appended CRC. In examples where the sync fieldis five-bits and each of data fields,, andare four bits, the sending sondecomputes the CRC on the 17 data bits from first separatorto separator, i.e. the whole frame apart from the CRC itself and the separator bits. In the particular example provided here, the CRC fieldcan be four bits generated by a polynomial, for example the polynomial 0x03=x4+x+1. In some embodiments, there is no seed value or XOR. Consequently, the CRC of an error-free 21-bit frame equals zero.
8 FIG.C 8 FIG.B 8 FIG.C 6 6 FIGS.A andB 6 6 FIGS.A throughD 850 802 850 0 802 804 0 1 0 1 0 1 806 2 6 1 6 7 808 7 6 6 7 6 7 850 802 802 802 804 illustrates that data symbol streamthat corresponds with the data frameillustrated in. As illustrated in, data symbol streambegins at symbol DS, which is also the last data symbol in the previously transmitted frame. The separator, which as discussed above is a 0, is illustrated in the data symbol transition between DSand DSaccording to that discussed above with(i.e. if DSis a data symbol of N-states then DSis a data symbol of P-states and if DSis a data symbol of P-states then DSis a data symbol of N-states). Since synchronization fieldis a series of 1's, then DSthrough DSare all the same as DS. DSto DS, however, designates separator, which is a 0 bit, and therefore DSis a data symbol that is the complement of DS(i.e. if DSis a data symbol of N states, then DSis a data symbol of P states whereas if DSis a data symbol of P states, then DSis a data symbol of N states). The data symbols in data symbol seriesare then designated to corresponded to the remaining bits in data frameaccording to the bit representations illustrated in. The last data symbol in data frameis then DSN, which in a 26 bit data frame N=26. The last data frame DSN is then the data frame that starts the next transmitted frame, where separatorof the next frame is represented by the transition between data symbols DSN and DS(N+1).
804 806 802 802 802 8 FIG.B 8 FIG.C 6 6 FIGS.A throughD Consequently, a receiver can synchronize with the data transmission. The receiver locates a separatorfollowed by synchronization fieldin the bit stream, which will identify the beginning of a data frame. As discussed above, in the particular example illustrated inand discussed above, the bit sequence “011111” uniquely identifies the beginning of a data frameand cannot occur elsewhere in data frame. Once synchronized, a receiver can then continuously receive data frames according toand the transitions discussed in.
3 FIG.B 300 334 334 304 306 310 312 312 As illustrated in, receivercan process data from antennato demodulate data transmitted as discussed above. As discussed above, antennacan be a triaxial antenna. The signals from antennasandare processed by AFEand digitized to input to digital processing. As discussed above, much of the demodulation process can be achieved in digital processing.
9 9 FIGS.A andB 3 FIG.B 9 FIG.A 9 FIG.B 9 FIG.A 334 1 2 900 950 900 illustrate an example of phase coherent narrow band digital signal processing, which determines a magnitude and phase of one of the three signals from antennaillustrated in(i.e. BH, BH, and BV).illustrates a narrow band decimating filter.illustrates a local oscillator tracking circuitthat can be used with filterof.
9 FIG.A 9 FIG.A 3 FIG.B 902 310 1 2 322 302 As illustrated in, an analog-to-digital converter (ADC), which is part of the AFE of AFE, provides digital data from a given CODEC ADC channel from one of the signals BH, BV, or BH, here labeled B. The remaining components illustrated inare aspects of one of the corresponding one of the signal processingas illustrated in. It should be noted that other antennas in wandmay include antennas that produce any number of magnetic signals that can be processed in a similar fashion as that described here.
902 904 904 902 904 906 904 908 906 908 0 9 FIG.A 9 FIG.A The sampling rate at ADCcan be anything from 10 kHz to 192 kHz—the typical bands for a Sigma Delta Audio Codec. A numerical oscillatorcan provide stable and phase-locked sine and cosign outputs at the carrier frequency f. Numeric oscillatorcan operate similar to that described in U.S. Pat. No. 4,285,044. As shown in, the digitized data signal from ADCis mixed with a sine output of numeric oscillatorin mixerand mixed with a cosine output of numeric oscillatorin mixer. Consequently, the output signals from mixersandprovide in-phase and quadrature signals for processing. The algorithm exhibited in, therefore, uses complex signals (In Phase and Quadrature Phase), which allows phase information to be carried through to the output.
906 908 906 910 914 918 908 912 916 920 314 9 FIG.A The signals from mixersandare then down sampled.illustrates a SINC3 decimating stage. In the decimating stage, the output signal from mixeris processed through a SINC3 filter, a down sampler, and a low-pass filter. Furthermore, the output signal from mixeris processed through a SINC3 filter, a down sampler, and a low-pass filter. In some embodiments, the down sampling bandwidth, for example, can be in the region of 50 Hz to 150 Hz, which is suitable for user interface.
918 920 918 922 920 924 922 924 924 926 922 926 928 930 932 934 928 932 934 328 302 340 9 FIG.A 9 FIG.A 3 FIG.B Low-pass filtersandcan both be finite impulse response (FIR) filters that define the overall frequency response and bandwidth. For example, in some embodiments the frequency response of the FIR filters can be set to about 1 Hz. As is further illustrated in, the output signal from filteris input to amplifierand the output signal from filteris input to amplifier. Amplifiersandprovide gain normalization. As is further illustrated in, the output signal from amplifieris inverted in inverter. The in-phase and quadrature signals from amplifierand inverter, respectively, are input to combiner. The combined signal is input to processing blockwhere magnitudeand phaseare calculated from the in-phase and quadrature signals input to combiner. As shown in, signalsandare input to locate processingand, combined with similar signals from other antennas in wand, is used to locate sonde.
9 FIG.B 950 900 950 904 illustrates a local oscillator trackerthat can be used with decimating filter. Local oscillator trackerforms a closed loop integral control law, the output of which adjusts the numeric oscillatorby a small amount until the error is negligible. This allows the receiver to be frequency locked to the transmission waveform and is important for the data encoding scheme described in further detail below.
950 934 900 952 952 954 956 956 958 958 960 956 958 958 962 964 964 904 9 FIG.B 9 FIG.A 0 As illustrated in the example local oscillator trackerillustrated in, the phase output signalfrom decimating filteris differentiated in phase derivative block. The result of blockis amplified in amplifierand the result in input to integrator. The result of integratoris input to a combiner. The output signal from combineris delayed in delayand combined with the output signal from integratorin combiner. The output signal from combineris again delayed in delayand output to error correction. Error correctioncan be input to numeric oscillatorillustrated into adjust the average frequency fso that the average overall phase is minimal.
6 6 FIGS.A throughD 950 With the modulation scheme illustrated inabove, local oscillator trackerwill move the oscillators to the effective average of the two frequency components:
6 6 FIGS.A throughD avge nom As discussed above, the average of the frequency signals according to the modulation scheme illustrated in, the average frequency Fis the nominal frequency fof the locating signal tone.
10 10 FIGS.A throughC 10 FIG.A 9 FIG.A 9 FIG.A 9 FIG.A 9 FIG.A 9 FIG.A 1000 1000 900 334 906 908 906 1002 910 914 918 908 1004 912 916 920 1006 922 924 926 928 930 1006 932 934 Demodulation of data transmitted by embodiments of the present disclosure is illustrated in.illustrates a first stageof the demodulation process. First stageworks with narrow band decimating filteras illustrated in. As shown in, the digitized signal B, which one of the signals from an antenna such as antenna, is input to multipliersandand mixed with a cosine and sine signal to generate in-phase and quadrature signals. The signal from multiplieris input to SINC3 decimator, which includes SINC3 filter, down sampler, and low-pass filteras illustrated in. The signal from multiplieris input to SINC3 decimator, which includes SINC3 filter, down sampler, and low-pass filteras illustrated in. Processor, rectifier and polar compute, represent elements,,,, andillustrated in. As discussed previously, processoroutputs the magnitude and phase of the signal B (B[mag]and B[phi]) for further processing.
1000 906 1008 1002 908 1010 1004 10 FIG.A The first stageof the demodulation uses a simple cross multiply to generate a sub-carrier channel-effectively an intermediate tone, labelled BX[I] and BX[Q]. As is illustrated in, the output signal from multiplieris input to multiplierand mixed with the output signal from SINC3 decimatorto form the output signal BX[I]. Similarly, the output signal from multiplieris input to multiplierand mixed with the output signal from SINC3 decimatorto form the output signal BX[Q].
10 FIG.B 10 FIG.A 4 4 FIGS.A andB 1020 1022 1024 1026 1024 1026 sub sub sub sub sub avg The data encoding scheme described herein can be considered a frequency shift key arrangement. Consequently, the phase domain of the modulation appears as an orthogonal signal as represented by a Phasor on the Argand diagram. Accordingly, the demodulation uses a Vector Cross product of the Cartesian components as shown in. As illustrated in the example of second stage, the signals BX[I] and BX[Q] illustrated inare input to vector cross productto form a cross product signal. The cross product signal is then input to multiplierand multiplier. In multiplierthe cross product signal is mixed with the cosine signal f[cos] and in multiplierthe cross product signal is mixed with the sine signal f[sin]. The signals f[cos] and f[sin] are generated by a numeric oscillator that is running at the sub-carrier frequency. In this example it is notionally, the sub-carrier frequency fis the average, or nominal, frequency f/M. In the particular examples illustrated here, as illustrated above in, M=16. Consequently, in the specific examples discussed above, the sub-carrier frequency can be given by
1024 1028 1026 1030 1028 1030 1032 1032 10 FIG.B The output signal from multiplieris input to a SINC3 decimating filter. The output signal from multiplieris input to a SINC3 decimating filter. The output signals from SINC3 decimating filtersand, demod[I] and demod[Q] respectively, is input to rectifier circuit. As illustrated in, rectifier circuitoutputs the demodulated magnitude and phase.
1034 1034 4 4 FIGS.A andB 6 6 FIGS.A throughD The bandwidth used in the demodulation stage is set accurately to ensure it is sufficiently wide to pass the data-information bandwidth without degradation. The demodulated magnitude is fed to the data decoding processto determine the phase characteristics as described in. Data decoding processorcan then determine N-state or P-state characteristics, and ultimately the transitions between data symbols as described in.
10 10 FIGS.A andB 3 FIG.B 10 FIG.B 334 1 2 334 334 1 2 334 The example illustrated inuse a single magnetic field signal B, which can be one of the signals from antenna(BH, BH, and BV). As discussed above, antennacan be a triaxial antenna that includes three orthogonally oriented coils for measuring the magnetic field in three orthogonal directions. As illustrated in, antennaincludes two orthogonal horizontal coils that produces signals BHand BHrelated to the magnetic field strength in two orthogonal horizontal directions and a vertically oriented coil that produce signal BV related to the magnetic field strength in the vertical direction. In some embodiments, in order to improve the detection of the data signal, all of the signals from antennacan be used to demodulate the data signal in.
1 2 334 1000 1 1 1 2 2 2 1 334 334 2 334 1 2 1 2 10 FIG.A Each of the signals BH, BH, and BV from antennacan be processed through parallel first stagesas illustrated in. This provides signals BHX[I] and BHX[Q] corresponding to input signal BH, BHX[I] and BHX[Q] corresponding to input signal BH, and signals BVX[I] and BVX[Q] corresponding to input signal BV. BHX[I] is the In-Phase component of the Sub-Carrier tone derived from a horizontal-oriented coil of antenna. BVX[I] is the In-Phase component of the Sub-Carrier taken from the vertically oriented coil of antenna. BHX[I] is the In-Phase component of second horizontally oriented coil of antenna. BHX[Q], BVX[Q] and BHX[Q] are the quadrature components of signals BH, BV, and BH, respectively.
10 FIG.C 10 FIG.B 10 FIG.C 1 2 1042 1 2 1044 1020 334 As is illustrated in, the in-phase signals BHX[I], BVX[I], and BHX[I] are combined in summerto produce a combined signal BX[I]. The quadrature signals BHX[Q], BVX[Q], and BHX[Q are combined in summerto produce a combined signal BX[Q]. The combined signals BX[I] and BX[Q] are input into second stageas indicated in. Consequently,allows a method of performing the demodulation on all three (3) axes as measured in antennawithout causing contention or any loss of signal-to-noise ratio.
10 FIG.C 1022 On first inspection, it may be thought that the summation of signals as illustrated inwould add noise to the demodulation process as a consequence of increasing the overall noise aperture of the system. This has been shown not to be the case, the orthogonal nature of the vector cross product affected by cross producthandles this effectively and allows the demodulation process to run smoothly regardless of which antenna may be carrying the dominant signal.
11 FIG. 3 FIG.C 8 FIG.A 8 FIG.B 4 4 FIGS.A andB 5 5 FIGS.A andB 1100 340 1100 344 344 1102 1100 344 342 340 1104 802 1102 1106 802 1104 1108 1108 1110 344 346 348 1108 802 340 illustrates operationof a sondeas illustrated inaccording to some embodiments of the present disclosure. As illustrated, operationmay be executed by processor, at least partially according to instructions stored in a memory of processor. In stepof processor, processorreceives parameters from sensors. As discussed above, the data can include pitch and roll data for sonde, although other parameters may also be monitored. In step, a data frame such as data frameillustrated inis assembled to include data representing the parameters received in step. In step, based on the data framegenerated in step, a sequence of data symbols is generated according to that described in. In step, the sequency of frequency modulations as illustrated inandcorresponding to the data symbol sequence generated in stepis determined. Finally, in step, processorprovides input to driverto drive antennato transmit the magnetic symbol according to the modulation determined in step. As should be understood, the timing of these sequences is such that a continuous sequence of data framesis transmitted on the magnetic signal generated by sonde.
12 FIG. 3 3 FIGS.A andB 1200 300 300 9 9 10 10 10 312 illustrates operationof a receiveraccording to some embodiments of the present disclosure. Receiver, as illustrated in, includes components as illustrated inA,B,,B, andC. In particular, these operations may be executed by various aspects of digital processor.
12 FIG. 3 3 FIGS.A andB 3 FIG.B 1202 1200 300 340 300 344 1204 312 1200 As shown in, in stepof operationreceiverreceives the magnetic signal generated by sondewith a plurality of antennas. As illustrated in, each of the plurality of antennas may generate one or more signals associated with the magnetic field strength and direction at receiver. For example, as is illustrated in, one or more of the antennas, for example antenna, can be a triaxial antenna that receives signals according to the magnetic field strengths in two orthogonal horizontal directions and one vertical direction. In step, the signals from each of the antennas are processed and digitized and input to digital processor, which performs the remainder of the operations in operation.
12 FIG. 9 9 FIGS.A andB 312 1206 1208 300 340 As illustrated in, digital processorcan determine the magnitude and phase of each of the signals from each of the antennas in stepas is described with. In step, receivercan then determine the physical location of sondebased on the signals received from the plurality of antennas.
1210 1218 340 1210 1212 1212 300 10 10 FIGS.A throughC Stepsthroughdescribe demodulating the received signals from the antennas to recover the digital bit stream that was modulated onto the magnetic signal by sonde. In step, one or more signals from one of the antennas is demodulated as illustrated into determine the phase relative to the nominal signal. In step, from the phase determination, individual states are determined. As is discussed above, the states are M cycles designating an N-state or a P-state. In step, receiverdetects the transition from an N-state to a P-state or a P-state to an N-state, which indicates the beginning of individual states and from which the sequence of individual states can be determined.
1214 1214 8 FIG.B In step, the sequence of data symbols as illustrated incan be determined. Locating a 0 bit transition as has been accomplished in stepalso indicates the start of a data symbol. Consequently, the sequence of data symbols can be determined.
1216 1218 300 802 300 802 340 In step, from the sequence of data symbols, the bit stream can be determined. From a 0 transition, setting the demarcation between two states and also the demarcation between two data symbols, the data symbols are recovered. In step, receivercan then locate the synchronization field “11111” that indicates the beginning of a data frame. Once that is located, receiverthen recovers the series of data framesthat are being transmitted by sonde.
In the preceding specification, various embodiments have been described with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the invention as set for in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
December 10, 2025
April 23, 2026
Browse 5M+ US patents with plain-English claim translations and AI-generated analysis.